The Internet of Things (IoT) is a network in which various devices having specific capabilities of awareness, computing, execution, and communication are deployed to obtain information from a physical world, and a network is used to implement information transmission, coordination, and processing, so as to implement interconnection between people and things or between things. In brief, the IoT intends to implement interconnection and interworking between people and things and between things. The IoT may be applied to various fields such as a smart grid, intelligent agriculture, intelligent transportation, and environment monitoring.
The mobile communications standardization organization 3rd Generation Partnership Project (3GPP) has proposed a Narrow Band Internet of Things (NB-IoT) subject in RAN Plenary meeting #69. A single carrier frequency division multiple access (SC-FDMA) technology is planned to be used for uplink of the NB-IoT. To ensure that uplink data of different terminal devices can arrive at a base station side at the same time without interference to each other, a terminal device needs to perform a random access procedure before sending the uplink data. Specifically, the terminal device needs to send a random access signal over a random access channel.
In the prior art, a structure of a random access channel is shown in FIG. 1. In the random access channel, a specific duration is defined as a time unit, and two frequencies f0 and f1 are used. A terminal device sends a random access signal by using only one frequency within each time unit, and sends a random access signal by using another frequency within a next adjacent time unit. That is, there is only one frequency hopping interval “f1-f0” in an existing random access channel. Consequently, there are many limitations in actual applications.